This type of screw-driving device comprises a tubular casing coupled to the front end of the screwdriver, a slide member slidably fitted into the casing through a return spring, and a mechanism provided within the slide member to feed a screw-holding tape by one-pitch steps corresponding to the intervals between the adjacent screws on the tape. In such a tape feeding mechanism, a pin is provided on one side surface of a sprocket having a number of projections on both side edges of the outer periphery thereof, and the pin is fitted into a guide slot provided on one side surface of the tubular casing and extending obliquely and then parallel relative to the longitudinal direction of the casing.
When the slide member is pressed against a workpiece, the slide member is forced into the casing and the pin is moved along the guide slot to thereby rotate the sprocket by one-pitch steps corresponding to the distance between the adjacent screws on the tape, so that the screw-holding tape having the grooves fitted onto the sprocket is fed by one pitch. However, after the screw on the screw-holding tape is driven into the workpiece by the screwdriver being rotated, the pin of the sprocket is returned through the rectilinear section of the guide slot by the return spring within the casing and, then, passed through the inclined section of the guide slot; therefore, the sprocket will be rotated in the opposite direction by one pitch and returned to the original position. For this purpose, a wide variety of complicated mechanisms have hitherto been used to disconnect the interlock between the sprocket and the guide slot near the end of the return stroke.